Device for indicating variations in thread tension in sewing machines



Nov. 21, 1950 L. ROSEMAN DEVICE FOR INDICATING VARIATIONS IN THREADTENSION IN SEWING MACHINES 4 Sheets-Sheet 1 Filed Oct. 31, 1947INVENTOR. LEO RosEMEN,

BY M /%y ATTORNEY I. lolly/[7% Nov. 21, 1950 1.. ROSEMAN DEVICE FORINDICATING VARIATIONS IN THREAD TENSION IN SEWING MACHINES 4Sheets-Sheet 2 Filed 001;. 51, 1947 INVENTOR. I IE0 RosEMH H, ATTORNEYNov. 21, 1950 ROSEMAN DEVICE FOR INDICATING VARIATIONS IN THREAD TENSIONIN SEWING MACHINES 4 Sheets-Sheet 3 Filed Oct. 31, 1947 INVENTOR. 1%Rossmmk.

A TTORNEY Nov. 21, 1950 ROSEMAN DEVICE FOR INDICATING VARIATIONS INTHREAD TENSION IN SEWING MACHINES 4 Sheets-Sheet. 4

Filed Oct. 31, 1947 INVENTOR. "LE0 RosEmHN,

7 ATTORNEY Patented Nov. 21, 1950 DEVICE FOR INDICATING VARIATIONS INTHREAD TENSION IN SEWING MACHINES Leo Roseman, Newark, N. J.

Application October 31, 1947, Serial No. 783,251

27 Claims. 1

This invention relates in general to sewing machines, and moreparticularly to machines of the types that include bobbins, shuttles orthe like, and one object of the invention is to provide a novel andimproved mechanism for automatically indicating, or for performing someother operation or producing some result upon, a change in the tensionof a thread or in the relative tension of two threads, for example, thebobbin and needle threads, during operation of the machine.

Another object is to provide in machines of the character described, anovel and improved means for automatically changing the tension of athread at a predetermined time or at a predetermined portion of thelength of the thread, so that the change in tension may be utilized forany desired purpose, for example, to indicate the approaching exhaustionof the bobbin thread.

A further object is to provide a thread having at least a portionthereof treated or constructed in a novel and improved manner, incombination with parts of a sewing machine or other machine in which thethread is used, to automatically change the tension of the thread,whereby said a change in tension may be utilized for actuating a signalor any other desired means.

Another object is to provide novel and improved means in such sewingmachines whereby the operator may be warned of excessive tension on theneedle thread.

Still another object is to provide in a sewingmachine novel and improvedmechanism for in.- dicating or producing a warning of imperfectstitching on the underside of an article being sewn, thereby eliminatingthe necessity for the operator to periodically turn over the work andvisually inspect the underside thereof.

Other objects, advantages and results of the invention will be broughtout by the following description in conjunction with the accompanyingdrawings, in which Figure 1 is a fragmentary schematic perspective viewof a portion of a sewing machine embodying my invention, showing the bedplate, the bobbin mechanism, the throat plate, the presser foot and theneedle;

Figure 1a is a fragmentary top plan view of the throat plate and aportion of the bed plate;

Figure 2 is a schematic perspective view of the head end of a sewingmachine embodying my invention and illustrating the normal stitchingoperation on a piece of work;

Figure 3 is a similar'view, with portions emitted, indicating theoperation when a change in the relative tensions of the bobbin threadand needle thread occurs;

Figure is an enlarged sectional side elevational view of the bobbin andits case that are illustrated in Figures 1-3, inclusive, the bobbinFigure 5 is an enlarged perspective view of the underside of the throatplate illustrated in Figure 1 and having my invention embodied there-1n;

Figure 6 is a similar view, with portions omitted for clearness inillustration;

Figure '7 is a fragmentary vertical sectional view, approximately on theplane of the line 'l'l of Figure 6, showing the parts in normaloperating position;

Figure 8 is a similar view, showing the position of the parts when achange in the thread tension occurs;

Figure 8a is a fragmentary vertical sectional view, approximately on theplane of the line ila8a of Figure 8;

Figure 9 is an enlarged schematic fragmentary perspective view of aportion of the mechanism embodying the invention, showing the partsduring operation of the machine with normal thread tension, as shown inFigure 2;

Figure 19 is a similar view, showing the position of the parts when achange in the thread tension occurs, as illustrated in Figure 3;

Figure 10a is a fragmentary top plan view of the mechanism shown inFigure 10 and illustrating the threads in horizontal cross-section;

Figure 11 is a View similar to Figure 10, showing the operation of theparts by a protuberance on the thread;

Figure 12 is a view similar to Figure 5, showing a modification of theinvention, with the parts in normal position;

Figure 13 is a similar view, showing the parts in the positionsresulting from a change in the thread tension;

Figure 14 is a top plan view of a modified form of the mechanismembodying th invention;

Figure 15 is an enlarged bottom plan view thereof;

Figure 16 is a fragmentary bottom plan view of the mechanism shown inFigure 13, with portions broken away and showing the parts in normalposition;

Figure 17 is a similar view, showing the parts in a position assumedafter a change in the thread tension;

Figure 18 is a fragmentary plan View of a thread having one form ofmeans for causing a change of tension in the thread during a sewingoperation;

Figure 19 is a similar view, showing another form of the thread;

Figure 20 is an enlarged fragmentary longitudinal vertical sectionalview through a partially wound bobbin that embodies other means forvarying the tension on the bobbin thread;

Figure 21 is a transverse vertical sectional view, approximately on theplane of the line 2i-2l of Figure 20;

Figure 22 is an enlarged transverse vertical sectional view through thebed plate of a sewing fcat'ed at 22.

3 machine having a modification of my invention applied thereto;

Figure 23 is an enlarged bottom plan view of the throat plate shown inFigure 22;

Figure 24 is a similar view of the throat plate, with portions brokenaway and showing the parts in normal position;

Figure 25 is a like View, showing the partsin the position assumed upona change in the bobbin thread tension, and

Figure 26 is a fragmentary plan view of a piece of work showing aneffect of an increase in the tension of the bobbin thread.

For the purpose of illustrating the principles oi the invention, 'I'have shown it in conjunction with a'known type of lock stitch sewingmachine whichincludes the usual bed plate I from which upwardly projectsthe main frame or 'gooseneck 2in which is mounted a thread takeup lever3, a needle thread tension device 4, and a reciprocable needle bar 5which carries the usual needle 6 through the eye of which the needlethread I is threaded to cooperate with a bobbin thread 8 that is woundon a bobbin 9 which is mounted in a bobbin case 10 supported by theusual bobbin rcase holder 1! beneath the bed plate of the machine.Athroatplate I2 is removably mo'u'nted on the bed plate beneath theneedle, as usual, and has a needle hole I 3 and a plurality of slots 1-4through which projects the usual feed dog of the work-feed mechanism if,some of which has been omitted because it forms no part of the presentinvention. For a purpose to be later described in detail, the needlehole it has a lateral by the usual mechanism which has not been shown.In order that my invention may be more clearly understood, it isdesirable to describe briefly the normal operation ofthe'sewing'mechanismgand with'reference to Figures 1 and '2, it will beunderstood that the needle, as it descends through the work 23 and theneedle hole 13 in the throat plate,'carries-the needle thread downwardlyand the sewing hook IS picks up the needle thread and loops it aroundthe bobbin thread to interlock the two threads, as best shown in Figure2; and as the needle rises, theneedle threadloop 2 I is pulled upwardly,and thereafter the takeup lever 3 exerts further tension -on-theneedle'thread so as to complete a stitch wherein the'needle and bobbinthreads interlockat about the center of the thickness of the work, asindi- In normal operation and with proper tension on the needle andbobbin threads exerted by the respective tension devices 4 and '18, thebobbin thread hugs the needle hole wallin the direction of feed of thework, and the needle thread loop pulls the interlocked bobbin threadtoward the center of the needle hole I3 and straight upwardlytherethrough. However, should the tension on the bobbin thread becomeexcessive relatively to the tension on the needle thread, the dragexerted by the bobbin thread will pull the needle thread loop 2| in thedirection of feed of the work, as best shown in Figure3, and theinterlock between the bobbin thread and the needle thread occurs on thebottom side of the work, as indicated at 23, thus causing faulty orimperfect stitching.

In accordance with my invention, means is provided to indicate thevariation in the relative tensions on the bobbin thread and the needlethread or to cause some operation or the production of "some result inaccordance with such variation, for example, to warn of faulty stitchingor of the approaching exhaustion of bobbin thread.

Referring particularly to Figures 1-10, inclusive, a-mechanismresponsive to variations in the relative tension of the two threads orto an increase in tension in the bobbin thread, is mounted on theunderside of the throat plate 12. form of the invention shown, thismeans comprises a fixed jaw 24 on the underside of the throat plate atone side of the needle hole 13, and a movable jaw 2 5 which is pivotallymounted 'ona stud 26-on the throat plate to cooperate with the fixedjaw. These two jaws have complemental notches 2! 'in their juxtaposededges, which, when said jaws are in one relation to eachother, form-ahole in register with the needle hole l3 through which the needle threadloop and "interlocked bobbin thread may normally freely pass, asshown"in "Figures 2, '6 and 9. The juxtaposed edges 28 0f the jaws outwardlyfrom the pivot "26 are normally in contact with each other "or so spacedthat should the needle thread and the bobbin thread located therein or aplurality'of thicknesses of thread disposed in a plane transverse of thespace between'the jaws, "as shown in Figures 10 and 10a, be pulledbetween the jaws, the movable jaw will be swung'about its pivot awayfrom the fixed jaw. Accordingly, should the tension on the bobbin thread"become excessive relatively to the tension of the 'needle thread, asshown in Figur'e'3, the needle thread loop 21 and the bobbin thread 8will be pulled simultaneously between said edge "portions 18 of thejaws, and there being then at least 'two thicknesses of thread betweenthe jaws, the movable jaw will be swung away from the fixed jaw, asshown in Figure 10. It will be observed that the slot [6 in the needlehole l3'offthe throat plate will-perlimit such movementof the threadsbetween the jaws, and a cover'plat'e [2a is secured to'theunderside ofthe throat plate over the jaws and has a hole l2'b "corresponding inshape to the needle hole l3. 7

'This movement of the movable jaw may be utilized to control any "otherdesired operation,

but, asshoWhJthe movable jaw has an angularly extending arm 29 which'i's'normally pressed by a spring 3|] so 'as'to yieldingly'hold themovable jaw 25 in normal position, When the jaw is in this position, adetent tooth3l carried'by a detent lever 32 normally bears against oneside of the arm 29., as shown in Figure 7, being "springpressed by asuitable spring '33, one end of which is secured in a bracket '34depending from the throat plate and in which' 'lthe de'tent lever32 ispivotally mounted at oneend, as indicated at 35.

In the Preferably, the detent tooth 3| is adjustable, and for thispurpose it is shown as carried by a channel-shaped piece 38 which has anadjustable bolt and slot connection 39 with the detent lever 32. It willbe observed that the projection of the end 36 of the detent leverupwardly through the throat plate upon variation in the thread tension,will serve as a signal or warning of said tension change. If desired,other visible or audible signals may be provided. For example, anelectrical contact element 40 may be mounted on the bracket 3 inelectrically insulated relation to the bracket and the throat plate andhave a binding post or the like ll for connection in an electriccircuit. This contact element is shown as having acontact finger 52 thatunderlies the head of the bolt 39 on the detent lever 32, so that whenthe machine is operating normally, said bolt head will be out of contactwith the finger 42, as shown in Figure 5, while when the change in thethread tension occurs, the bolt head will engage the contact finger 42,as shown in Figure 8a. The bolt head may be grounded in an electriccircuit. Thus, by connecting the contact element as and the bolt 39 inan electrical circuit with a source of electricity and a signal or otherdevice, the signal or device will be actuated upon a change in therelative tension of the needle and bobbin threads.

It may be desirable to adjust the movable jaw 25 relative to the fixedjaw 2t, and thus I may mount a slidably adjustable stop plate 43 on theunderside of the throat plate to form an abutment for the arm 29 to holdthe jaw 25 in predetermined spaced relation to the jaw 2s. justment maybe particularly desirable to accommodate the use of threads of differentdiameters.

It will be observed that this mechanism will indicate the change intension regardless of the cause of the change which may result eitherfrom loosening of the tension of the needle thread or increase in thetension of the bobbin thread as the result of variation of the springpressure exerted by the tension devices 4 and I8,

or as the result of varying diameters of the threads, or as the resultof a deliberate change in tension, for example, by treatment of thethread to cause increase in tension thereon as it passes beneath thebobbin spring ill, or by winding the thread at a certain point in such amanner as a to provide an increase in tension as the thread is unwound.

To deliberately cause a change in tension of the bobbin thread at apredetermined time or at a predetermined point in the length of thebobbin thread, the thread may have a knot tied therein,

-or friction-producing substances, such as soap,

crayons, waxes and numerous other substances applied thereto, or byattaching a friction-producing element to the thread, or by reversingthe winding of the thread on the bobbin at a certain point, or bypassing a convolution of the thread through a friction-producing elementon the bobbin during winding of the latter, and so on.

In Figure 13 is shown a piece of thread saturated with or having appliedthereto some friction-producing substance, such as soap, as indicated atM, while in Figure 19 a thread having an enlarged portion 45 is shown,and in Figure ll a thread having a knot 46 therein is illustrated.

With all of these forms of thread, when the portions at, 45 or 46 passbeneath the bobbin spring 53, the tension on the bobbin thread will besubstantially increased by the friction between the F spring and certainportions of the threads.

This ad- In Figures 20 and 21, one convolution of the bobbin thread 41is shown as slipped between a spring tongue #38 and one end flange 49 ofthe bobbin, so that as said convolutions pull from said tongue, thetension onthe thread will be increased. 1

A modification of the invention is shown in Figures 12 and 13. Inthisform of the invention, the structure is identical with thathereinbefore described with the exception that a different detentmechanism is provided for the arm 29. As shown, said arm 29 has a notch50 in one end thereof with which cooperates a detent tooth 5! that hasan adjustable screw and slot connection 52 with a detent lever 53, oneend of which is mounted on a shaft 54 that is journaled in a bearingbracket 55 in perpendicular relation to the throat plate l2. A torsionspring 56 has one end connected to said bracket and its other endconnected to the detent lever 53 so as normally to influence the detentfinger 55 toward the arm 29, as shown in Figure 12. When the movable jaw25 and its corresponding arm 29 are in normal position, the detent tooth5! abuts one end of the arm 29 and is held away from the notch 59, butwhen the jaw 25 is actuated upon a change in tension of the thread, thearm 29 is swung so that the detent tooth is snapped into the notch 50,as shown in Figure 13, so as to hold the arm in that position. An

electrical contact finger 51 is mounted on the lever 53 to cooperatewith another contact element 53 on the throat plate, so that saidcontact finger and contact element may be connected in an electricalcircuit for operating a signal or any other desired mechanism. The

shaft 56 may have a finger-piece 59 or any other tension mounted on itsunderside.

suitable means for rotating it to swing the detent lever 53 to itsnormal position to release the movable jaw 25 and to hold the contactfinger 51 out of engagement with the contact member 58.

Another modification of the invention is shown in Figures 14-17,inclusive, wherein the throat plate 6% has a needle hole Bl like thehole I3 and has means responsive to variations in thread As shown, thismeans comprises a lever 62 that is pivotally mounted intermediate itsends on a pin 63 to swing about a horizontal axis or in a planeperpendicular to the plane of the throat plate. One end portion of thelever has a hole 64 in approximate register with the needle hole 6! inthe throat plate, said end portion having a slit outwardly from saidhole of a width to permit free passage of only one thread at a time and.forming sprin arms 64a, and overlying said end portion of the lever isa cover plate 65 having a similar hole 66. The other end of the lever 62is normally actuated by a compression spring 61 so as to swing thefirst-mentioned end downwardly or away from the throat plate when thelatter is mounted in a sewing machine.

In operation, the needle loop and bobbin thread normally move throughthe holes Si, 64 and 66, but upon an increase in tension of the bobbinthread relatively to the needle thread, the loop is drawn into thenarrow ends of the holes 6|, 6'2 and 66 in such a manner as to swing thelever 62 into the position shown in Figure 17.

For controlling the operation of some other device, for example, toproduce a signal, a detent bar 68 may be slidably mounted in the throatplate so as to normally abut the edge of the spring-pressed end of thelever 62 when the latter is in its normal position, as shown in Fig-.1

are 16, said bar being normally influenced by a spring or other suitablemeans 69 in such a, manner as to slide beneath said spring-pressed endof the lever when the lever is actuated upon a change in thread tension,as shown in Figure 17. The rod 68 may be connected to an electric switchor any other suitable mechanism so as to actuate the latter upon slidinof the rod when the thread tension changes.

It will be observed that due to swinging of the lever 62 as the resultof the pulling of the needle loop into the narrow portion of the hole64, the position of the lever relative to said threads will change sothat the threads will clear themselves in the larger portion of the holewhen the lever has been swung to its limit, as shown in Figure 17.

From the foregoing, it will be understood that the device responsive totension will operate with the usual thread to indicate an increase inthe tension of the bobbin thread relative to the tension of the needlethread so as to, for example, warn of imperfect stitching. Also, bytreatment or special construction of the thread at predetermined points,as by saturating the thread with a friction-producing substance toincrease the frictional characteristics, or b tying a knot in thethread, the tension on the bobbin thread may be artificially increasedwhen said portion of the thread passes beneath the bobbin spring 18 at apredetermined time, so as to, for example, indicate the approachingexhaustion of the thread.

Furthermore, when the bobbin thread is specially treated or constructedso as to actuate a signal at a predetermined time during operation ofthe machine, for example, to indicate the approaching exhaustion of thebobbin thread, the failure of the signal to operate at saidpredetermined time or prior to the exhaustion of the bobbin threadwould, under otherwise normal conditions, warn the operator that theneedle thread tension is excessive.

It is also possible to utilize the device for detecting the presence ofknots or similar abnormalities in the bobbin .thread, even should theknot pass the bobbin spring without causing actuation of thetension-responsive mechanism and without any change in the tension onthe bobbin thread. In Figure 11 is shown a bobbin thread having a knot46 therein. During normal oper ation, the bobbin thread is normallypulled in the direction of work feed between the edges 28 of the jaws orinto the slotted portion of the hole 64 during each stitch formation,and therefore, a knot alone in the bobbin thread would actuate the jaw25 or the lever 62 upon passage of the knot between the jaws or throughthe slotted portion of the hole 64, respectively. Moreover, it should beunderstood that keyhole slots, although preferable, are not necessary tooperation of my mechanism, the keyhole shape being used mainly toprovide clearance for the thread to pass between the jaws 24 and 25 orthrough the lever 62, and consequently the shape of the holes may bevaried as desired.

As above indicated, soap is preferred for increasing thefliction-producing properties of the thread because it createssufficient tension to activate the jaws but not enough to causeunsatisfactory stitching; but almost any'other substance can be used ifthe tensions of the various springs, such as the bobbin tension springl8, springs 30 and El, and the space between the jaws 14- and 25, areproperly adjusted.

When a substance such as soap is applied to the thread, it is desirableto form a hole 10 in the bobbin tension spring 48 for scraping andreleasing the soap from the thread and preventing accumulation of excesssoap under the tension spring. Such an opening also will act as asnubber for knots in the thread to ensure that the tension on the threadis increased in the desired manner where knots or similar protuberancesare used instead of soap or the like.

Instead of or in addition to indicating the variation in thread tension,the treatment of the thread with soap or the like may also be utilizedfor rippling or puckering the work being sewed, as shown in Figure 22 ofthe drawing, where the reference character H designates normal stitchesin the work-piece 12, while the reference character 13 designatesshortened stitches that are caused by the excess tension on the bobbinthread and produce puckers or ripples 14 in the work.

The invention may also be embodied in mechanism that is actuated solelyby the bobbin thread and does not depend upon the needle thread loop foroperation. As shown in Figures 23-25, inclusive, the throat plate 15 hasa recess 16 on its underside in which an element 1'! responsivetovariations in the bobbin thread tension is longitudinally slidablymounted and is cover-ed by a cover plate 18 separably secured to thethroat plate by screws 19. The throat plate has a needle hole that maybe like the hole [3 and the cover plate 18 has a similarly shaped hole8!. An elongated slot 82 is formed in one end portion of the slide 11and this slide is normally yieldingly actuated by a spring 83 so thatthe end of the slot 82 in the direction of work feed is normally freelyengaged but not actuated by the bobbin thread when the tension on thelatter is normal, while when the bobbin thread tension becomesexcessive, the thread will be drawn laterally of the needle hole andagainst said end of the slot 82 so as to actuate the slide 11 in thedirection of the work feed and against the tension of the spring 83, asshown in Figure 25.

For controlling the operation of some other device, for example toproduce a signal, a detent bar 84 similar to the bar 68 shown in Figures14-17, inclusive, may be slidably mounted in the throat plate so as tonormally abut the edge of the slide 11 when the latter is in its normalposition, as shown in Figure 24, said bar being normally influenced by aspring or other suitable means 85 so as to slide behind the end of theslide TI when the latter is actuated upon a change in thread tension, asshown in Figure 25. The bar may be used to actuate an electric switch orany other suitable mechanism upon sliding of the "bar when the threadtension changes.

It is immaterial whether or not the needle thread loop is pulled by thebobbin thread tension against the end of the slot 82, because the slidell is actuated solely by the pull on the bobbin thread rather than bythe multiple thicknesses of the threads as in the other forms of theinvention.

It will be observed that in all forms of the invention the mechanism isshown as attached to the throat plate so that it can be easily andquickly applied to and removed from the machine by simple applicationand removal of the throat plate; but obviously, the mechanism may bemounted on the machine in other ways than by attachment to the throatplate. Moreover, while I have shown the invention as used in conjunctionwith a certain type of sewing machine, it

"can be adapted to other types by modification which would be apparentto one skilled in the art as necessary to accommodate the invention to aparticular machine. For example, the jaws may be placed on just one sideof the elongated needle hole of a known type of zig zag machine andactuated by stitches on only one side of the bite, i. e., at one end ofthe tranverse movement of the needle.

It will alsobe apparent to those skilled in the art that my inventionmay be used on either automatic constant speed machines or upon machinesin which the speed is frequently varied, and the invention has especialvalue in connection with the latter type or variable speed machines.

For the purpose of illustrating the principles of the invention, I haveshown several specific embodiments thereof, but it should be understoodthat the details of construction of the mechanism may be widely modifiedand changed within the spirit and scope of the invention.

Having thus described the invention, what I claim is:

l. The combination with a sewing machine in which during the sewingoperation a needle thread is passed through the work and formed into aloop around a bottom thread beneath the work and the portions of saidthreads at said loop normally follow a predetermined path and are drawnout of said path upon an excess in the tension on the bottom threadrelative to the tension of the top thread, of means actuated by saidportions of said threads when they are drawn out of said normal path byexcessive tension on said bottom thread for performing an operation uponoccurrence of said change in tension. I

2. The combination with a sewing machine in which during the sewingoperation a needle thread is passed through the work and formed into aloop around a bottom thread beneath the work and the portions of saidthreads at said loop normally follow a predetermined path and are drawnout of said path upon'a variation in the tension on one thread relativeto the tension of the other thread, of means engaged and actuated bysaidportions of said threads at said loop when they are drawn out of saidnormal path for performing an operation upon occurrence of said changein tension.

3. The combination as defined in claim 2, wherein said means comprisesan element including a movable part and having a clearance through whichsaid portions of said threads normally freely pass, said movable partbeing located so as to be actuatedwhen said portions of said threads aredrawn out of said normal path.

4. The combination as defined in claim 3 with the addition of means fornormally yieldingl-y influencing said part into a normal position, andwherein said part is actuated out of said normal position into anotherposition when said portions of said threads are drawn out of said normalpath, and detent means is provided for releasably holding said part inthe second mentioned position.

5. The combination as defined in claim 2, wherein the friction-producingproperties of said bottom thread are greater at a predetermined portionof its length than the other portions thereof, and with the addition ofmeans to'frictionally engage said'predetermined portion of said threadto increase the tension on the thread during the sewin operation. I

6. The combination as defined in claim .2,

wherein said sewing machine has a throat plate and said means is locatedon the underside of said throat plate.

7. The combination as defined in claim 2, wherein said means comprisestwo jaws one of which is movable relative to the othensaid jaws havingcomplemental notches to form between them normally an opening throughwhich said portions of said threads normally may freely pass, saidmovable jaw being actuated by movement of said thread portions laterallyout of said opening and between said jaws when said thread portion aredrawn out of said normal path.

8. The combination as defined in claim '7, with the addition of meansfor adjusting and holding said movable jaw in predetermined relation tosaid fixed jaw.

9. The combination as defined in claim 7, with the addition of meansnormally actuatingsaid movable jaw toward the fixed jaw, and anadjustable stop for limiting movement of said movable jaw toward thefixed jaw.

10. The combination as defined in claim "1, with the addition of meansnormally actuating said movable jaw toward the fixed jaw, a detent leverhaving a detent tooth to engage and hold said movable jaw when it isactuated away from said fixed jaw, and means adjustably mounting saiddetent tooth on said detent lever to compensate for difierent degrees ofmovement of said fixed jaw.

1. The combination with a sewing machine in which a top thread and abottom thread are interconnected normally under predetermined relativetensions to form stitches, of means engaged and actuated by said bottomthread upon a change in said relative tensions.

12. The combination with a sewing machine in which a top thread and abottom thread are drawn from respective sources of supply andinterconnected in work to form stitches with said threads underpredetermined relative tensions during normal sewing operations, ofmeans located between the source of supply of the bottom thread and thepoint of interconnection and engaged and actuated by a portion of atleast one of said threads upon a change in said relative tension forperforming an operation uponoccurrence of said change.

13. The combination with a sewing machine in which a top thread and abobbin thread are drawn from respective sources of supply andinterconnected in work to form stitches with said threads underpredetermined relative tensions during normal sewin operations, of meanslocated between the source of supply of the bobbin thread and the pointof interconnection and engaged and actuated by a portion of at least oneof said threads upon an increase in the tension of the bobbin thread forperforming an operation uponoccurrence of said increase.

14. The combination 'as defined in claim 12, wherein said sewing machinehas a throat plate and said means is located on the underside of saidthroat plate. I

15. The combination with'a sewing machine in which during the sewingoperation a needle thread and a bottom thread are drawn from respectivesources of supply andare interconnected in work to form stitches, of amovable part located between the'source of supply of said bottom threadand the point of interconnection of said threads, said part havingclearance to permit free passage thereby of not more than a L- certainnumber of thicknesses of thread simultaneously without actuation of saidpart and being actuated upon passage thereby of more than said certainnumber of thicknesses of thread at a time.

16. The combination as defined in claim 15, wherein said threadsnormally operate under predetermined tensions, and said movable part isactuated upon an increase in the tension of the bottom thread relativeto the tension of the top thread.

17. As an article of manufacture, a throat plate for a sewing machinehaving a needle hole, means on the underside of said throat plateincludin a movable part located adjacent said needle hole, said parthaving clearance to permit free passage thereby of a single thickness ofthread without actuation of said part and being actuated upon passagethereby of more than one thickness of thread.

18. As an article of manufacture, a throat plate for a sewing machinehaving a needle hole, means on the underside of said throat plateincluding av movable part located adjacent said needle hole and normallyinactive, said part being actuated upon abnormal movement of a threadlaterally of said hole in one direction.

19.. Asan article of manufacture, a throat plate for a sewing machinehaving a needle hole, means on. the underside of said throat plateincluding a movable part located adjacent said needle hole, said parthaving clearance to permit free passage thereby of not more than acertain number of thicknesses of thread simultaneously without actuationof said part and being actuated upon passage thereby of more than saidcertain number of thicknesses of thread at the same time.

20. As an article of manufacture, a throat plate for a sewing machinehaving a needle hole, means on the underside of said throat plateincluding a movable part located adjacent said needle hole, said parthaving clearance to permit free passage thereby of two thicknesses ofthread simultaneously without actuation of said part and being actuatedupon passage thereby of more than said two thicknesses of thread at thesame time.

21. An article of manufacture as defined in claim 18, wherein saidmovable part is provided with a thread hole that has a large portion anda small portion communicating therewith so that a plurality ofthicknesses of thread may pass simultaneously through said large portionwith out actuating said part but attempted passage of said thicknessesthrough said small portion will actuate said part.

22. The combination with a lockstitch sewing machine havingstitch-forming devices including a needle, a loop taker, a wound lockingthread supply about which the loop taker passes each loop of needlethread and which is unwound and interlocked at a certain point with saidneedle thread during operation of said machine with said needle threadand said locking thread under predetermined relative tensions, of meanslocated between said locking thread supply and said point ofinterlocking and responsive to change in the relation of said tensionsfor performing an operation upon the occurrence of said change.

23. The combination with a lockstitch sewingmachine havingstitch-forming devices including a. needle, av loop taker, a woundbobbin thread supply about which the loop taker passes each loopofneedlethread and which is unwound and interlocked at a certain pointwith said needle thread. during operation of said machine with;

said needle thread and said bobbin thread under predetermined tensions,of means responsive to an increase in the tension of said bobbin threadfor performing an operation upon the occurrence of said increase.

24. The combination with a lockstitch sewing machine havinstitch-forming devices including a needle, a loop taker, a wound bobbinthread supply about which the loop taker passes each loop of needlethread and which is unwound and interlocked at a certain point with saidneedle thread during operation of said machine with said needle threadand said bobbin thread under predetermined relative tensions, of meanslocated between said bobbin thread supply and said point of interlockingand including a movable part directly engaged and actuated by at leastone of said threads upon a change in the relation of said tensions forperforming a certain operation.

25. The combination with a lockstitch sewing machine havingstitch-forming devices including a needle, a loop taker, a wound lockingthread supply about which the loop taker passes each loop of needlethread and which is unwound and interlocked at a certain point with saidneedle thread during operation of said machine with said needle threadand said locking thread under predetermined relative tensions, of meansincluding a movable part directly engaged and actuated by said lockingthread upon a change in the relation of said tensions for performing acertain operation, and means controlled by said movable part forindicating said change.

26. The combination with a lockstitch sewing machine havingstitch-forming devices including a needle, a loop taker, a wound lockingthread supply about which the loop taker passes each loop of needlethread and which is unwound and interlocked at a certain point with saidneedle thread during operation of said machine and the portions of saidthreads at said loop normally follow a predetermined path and are drawnout of said path upon a variation in the tension on one thread relativeto the tension of the other thread, of means engaged and actuated bysaid portions of said threads when they are drawn out of said normalpath for performing an operation upon occurrence of said change intension.

27. The combination with a sewing machine in which during the sewingoperation a needle thread is passed through the work and interconnectedwith a bottom thread with said bottom thread under predeterminedtension, of means ben ath the work engaged and actuated by a portion ofat least one of said threads upon a change in said tension upon thebottom thread.

LEO ROSEMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

